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Kaplan MCAT Biology > Digestive System: Ingestion and Digestion (HY) > Flashcards

Digestive System: Ingestion and Digestion (HY) Flashcards

1
Q

what does the alimentary canal consist of (path of the digestive tract)?

A

oral cavity (mouth) –> pharynx –> esophagus –> stomach –> small intestine –> large intestine –> rectum

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2
Q

What types of digestion occur in the oral cavity?

A
  1. mechanical digestion: through mastication (chewing) and saliva (lubricates); increase surface-to-volume ratio
  2. chemical digestion: through enzymes in saliva (starts in mouth and ends in small intestine)
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3
Q

what are the two enzymes in saliva and what do they do?

A

salivary amylase: hydrolyzes starch

lipase: hydrolyzes lipids

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4
Q

How is saliva production triggered?

A

food in mouth or sight/smell of food –> parasympathetic neural circuit –> three salivary glands produce saliva

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5
Q

what is a bolus?

A

the clump of food that our mouth forms and send to the pharynx

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6
Q

what two structures does the pharynx connect to?

A
  1. esophagus (digestive tract)

2. larynx (respiratory tract)

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7
Q

what are the three parts of the pharynx/

A
  1. nasopharynx
  2. oropharynx
  3. laryngopharynx
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8
Q

what is the epiglottis?

A

structure that prevents food from going down the respiratory tract

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9
Q

what is peristalsis?

A

rhythmic contraction

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10
Q

reversed peristalsis in the digestive tract (not down the digestive tract) results in what?

A

emesis or vomiting

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11
Q

the top and bottom of the esophagus are under what type of nervous control?

A

top: somatic motor control (voluntary)
bottom: parasympathetic nervous control

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12
Q

which part of the pharynx initiates swalling?

A

oropharynx

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13
Q

what is the approximate capacity of the stomach?

A

2 liters

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14
Q

what are the two glands contained in the mucosa (stomach mucous membrane)?

A
  1. gastric glands

2. pyloric glands

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15
Q

how is the gastric gland activated?

A

sight/taste/smell of food –> parasympathetic nervous system (vegas nerve) –> gastric gland

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16
Q

what are the three types of cells in the gastric gland?

A
  1. mucous cells
  2. chief cells
  3. parietal cells
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17
Q

what do mucous cells do in gastric glands?

A

produce bicarbonate-rich mucus

this mucus protects muscular stomach wall from harsh acid (pH = 2) and proteolytic environment in the stomach

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18
Q

what two cell types secrete gastric juice?

A

chief cells and parietal cells

19
Q

what type of zymogen do chief cells secrete?

A

pepsinogen

20
Q

what do parietal cells secrete to cleave pesinogen?

A

secrete hydrochloric acid, and hydrogen ions cleave pepsinogen

21
Q

where does pepsin cleave peptides?

A

cleaves peptide bonds near aromatic amino acids

22
Q

what is intrinsic factor secreted from parietal cells?

A

glycoprotein involved in absorption of vitamin B12

23
Q

in what pH is pepsin active?

A

very low acid pH (stomach is pH = 2)

24
Q

what type of cells do pyloric glands contain?

A

G-cells

25
Q

what do G-cells serete?

A

gastrin, a peptide hormone

26
Q

what does the peptide hormone gastrin induce?

A
  1. induces parietal glands to secrete more HCl

2. signals stomach to contract and mix contents

27
Q

what is chyme?

A

the acid, semifluid mixture in the stomach consisting of digested solid food

28
Q

what are the six products that the stomach secretes?

A
  1. HCl: kills microbes, pepsiongen–>pepsin, denatures proteins
  2. pepsinogen
  3. mucus: protects mucosa (mucose membrane)
  4. bicarbonate: in the mucus and protects mucosa
  5. water
  6. intrinsic factor: absorption of vitamin B12
29
Q

what are the three segments of the small intestine in order from first to last?

A
  1. duodenum
  2. jejunum
  3. ileum
30
Q

what are brush-border enzymes (function, location)

A

break down dimrs and trimers of biomolecules into absorbable monomers
they are present on surface of cells lining duodenum

31
Q

for lactose intolerance, why does bloating, flatulence, and diarrhea occur?

A

lack of lactase enzyme (a disaccharidase) to digest lactose (a dimer of glucose and galactose). undigested dimer is digested by bacteria, producing methane. dimer also can pull water into stool.

32
Q

what does aminopeptidase do in small intestine?

A

removes N-terminal amino acid from protein

33
Q

what do dipeptidases do in small intestine?

A

cleave peptide bond of dipeptide (2 amino acids)

34
Q

enteropeptidase activates which zymogen in small intestine?

A

enteropeptidase activates trypsinogen to trypsin

35
Q

what is secretin in small intestine?

A

a peptide hormone that

  1. causes pancreatic enzymes to be released in duodenum and
  2. regulates pH by reducing HCl secretion and increasing bicarbonate secretion
36
Q

what is cholecystokinin (CCK) in small intestine?

A

a peptide hormone that

  1. stimulates release of bile and pancreatic juice
  2. promotes satiety in the brain
37
Q

what are the three components of bile in small intestine?

A
  1. cholesterol
  2. bile salts (derived from cholesterol)
  3. pigments
38
Q

what do bile salts do in small intestine?

A

amphilic molecules that act like detergents in mechanical digestion
specifically emulsify fats and cholesterol

39
Q

when bile salts emulsify fats and cholesterol, what forms in small intestine??

A

micelles

40
Q

what is the purpose of fats and cholesterol forming micelles in small intestine?

A

without emulsifying with cholesterol and forming micelles, fat would precipitate out of aqueous mixture in duodenum and wouldn’t be digestable by lipases. micelles also increase surface area of fat for digestino by lipases

41
Q

what is pancreatic juice?

A

bicarbonate-rick alkaline solution with enzymes

bicarbonate neutralizes acidic chyme

42
Q

at which pH are most digestive enzymes in the duodenum active?

A

pH = 8.5

43
Q

ultimately, parasympathetic stimulation to release two peptide hormones in duodenum (CCK and secretin) does what?

A

release enzymes, bicarbonate, and fluid (pancreatic juice)

Kaplan MCAT Biology (14 decks)

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